I'm just about to embark on installing the heating system for our house
refurbishment.

For my upstairs radiators, I intend to use a polypipe manifold in the
airing cupboard to transition from 22mm copper into 15mm plastic and
then bring the pipes through the floor joists without joins to under the
radiators, then come up to the radiator valves in 15mm copper. The
advantage of this approach is an easier installation and fewer
inaccessible joints.

My question is, what joint to use for the bend between the plastic pipe
running horizontally and the 15mm copper radiator tail? There seems to
be a choice between brass compression and using one of the plastic
pushfit bends. I'm worried that the pushfit joints won't be reliable and
we'll end up with leaks into the ceiling after a few years.

What are there pros/cons?